1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more specifically, to a method of manufacturing a semiconductor device, called a chip-size package, which is suitable for high-density packaging.
2. Description of the Prior Art
Various types of semiconductor devices have been developed for satisfying demands to electronic devices, such as, reduction in size and weight, speed-up and multi-functionalization thereof. Demands for increasing the number of pins due to the high integration of the semiconductor chips and for reduction in size and thickness of the semiconductor devices have been getting stronger so that the fine-pitch arrangement of the pins is essential for satisfying both demands. Thus, it is considered that the inner-lead connection which can narrow pitches of the pins and the area-array connection which can enlarge pitches of the pins, be the essential techniques.
A chip-size package-type semiconductor device is in the form of a semiconductor chip and a carrier film which are integrally bonded by means of an adhesive film. One side of the semiconductor chip, which is attached to the carrier film, is formed with a plurality of electrode pads along the edge thereof. On the other hand, the carrier film includes an organic insulating film and wiring layers formed on the organic insulating film. Each of the wiring layers includes a region for connection to the corresponding electrode pad of the semiconductor chip. Further, a plurality of bump electrodes are formed as electrode pads of the carrier film for connection to the exterior. The bump electrodes are arranged in a grid at regular pitches and distributed widely on a side of the organic insulating film remote from the wiring layers. The wiring layers are provided on a side of the carrier film facing the semiconductor chip. Each of the wiring layers has one end connected to the corresponding bump electrode through a via hole which is formed by filling a metal material into a through hole formed at the organic insulating film. Other through holes are further formed at the carrier film, and the metal material is filled into these other through holes so as to form via holes, each for connection between the wiring layer and the electrode pad as inner leads. Each via hole is adjustable in position, when formed, relative to the electrode pad and the wiring layer. The inner-lead connection of the electrode pad and the wiring layer is achieved through this via hole.
The chip-size package-type semiconductor device is, in general, fabricated in the following manner:
After temporarily attaching the adhesive film to either one of the semiconductor chip and the carrier film, the electrode pads and the wiring layers are electrically connected to each other. Subsequently, the adhesive film is bonded to the other of the semiconductor chip and the carrier film by applying heat and pressure. Thus, a size of the adhesive film is limited to a size corresponding to an area defined within the electrode pads, that is, not corresponding to all the area of the joint surface of the semiconductor chip, so as to avoid overlapping the electrode pads.
However, in such a fabricating method, setting or positioning of the adhesive film relative to the semiconductor chip is difficult. Further, since the adhesive film is not interposed between the semiconductor chip and the carrier film at regions along the edge of the semiconductor chip, sealing therebetween tends to be insufficient. When the sealing is insufficient, moisture proof is deteriorated, thus leading to insulation failure and further to reduction in life duration of the semiconductor device.
Further, in this kind of the chip-size package-type semiconductor device, it is important that a diameter of each of the through holes formed at the organic insulating film be set as small as possible for rendering a pitch of the bump electrodes 24 as small as possible. In general, the through hole is formed by the chemical etching or the laser processing using the excimer (KrF) laser. The excimer laser is used because it is difficult to achieve the fine processing using the well-known YAG laser. However, it is also difficult to achieve the fine processing even using the chemical etching, and further, although the excimer laser can achieve the fine processing, its oscillating tube is expensive and its maintenance cost is high so that it is difficult to use the excimer laser.
Under these circumstances, in the conventional processing method, a diameter of the through hole is 50 .mu.m at minimum. Further, a shape of the through hole is tapered. Thus, narrowing of the pitches of the through holes is limited.